The present invention relates to a mechanism or device for transferring a torque to a hammer drill tool and/or another tool of a hand tool apparatus and to a tool and tool holder that uses the device.
A device for transferring torque to a hammer drill tool and/or another tool of a hand tool apparatus is known and comprises a tool member having a tool shaft provided with a plurality of catch grooves in the tool shaft, open at the tool shaft end received in the tool apparatus and provided with at least one elongated locking groove circumferentially displaced from the catch grooves in the tool shaft; a tool holder having a tool receptacle provided with a receptacle cavity in which the drill tool is held in operation, wherein the tool receptacle has at least two axially extending, advantageously diametrically opposed, catch elements projecting inwardly into the receptacle cavity and engageable with respective catch grooves in the tool shaft and also having at least one lock element in a radial recess in the tool receptacle provided in a circumferential region of the receptacle cavity spaced from the catch elements and engageable in the at least one locking groove and the at least one locking groove is shaped to limit the axial motion of the tool when the at least one lock element is engaged in the at least one locking groove; and means for engaging and retaining the at least one lock element in the at least one locking groove.
One such device is described in German Open Patent Application DE-OS 25 51 125 in which two opposing catch elements are provided in the receptacle cavity of the tool holder, which engage in corresponding catch grooves provided in the tool shaft. Furthermore two similar opposing lock elements displaced 90.degree. from the catch elements are provided, which lock radially into corresponding elongated locking grooves in the tool shaft and which guarantee that the axially slidable tool, e.g. a hammer drill bit or chisel bit, does not fall out and/or is not unintentionally pulled out of the tool holder.
Since this tool holding system known as "SDS-plus" is used for percussion drilling machines and hammer drill tools and for various tools of different power insertable in their tool holders, a single shaft diameter and also a single receptacle cavity diameter of about 10 mm, for example, are required for compatibility of the different tools. This has the disadvantage that the higher powered tools used in the correspondingly higher powered apparatus can be used for only a limited time in continuous operation under full load, because the torque transferring device becomes severely worn. The torque transmission occurs by engagement of only two comparatively small opposing side surfaces of the catch grooves and the inwardly projecting catch elements or catches--the so-called torque transferring device.